US Patent 11,638,692: Vancomycin Oral Liquid Formulation Claims and Patent Landscape

US Patent 11,638,692 covers a non-sterile, homogeneous oral liquid formulation containing vancomycin hydrochloride, water, an approved buffer, and a specified preservative. The formulation must have a pH of 2.5 to 4.5 and remain stable for at least one week at ambient and refrigerated temperatures. Claims 5 through 9 narrow the invention to citric-acid formulations, with claim 9 requiring no flavoring agent. The estate is technically narrow but commercially relevant to ready-to-use or extemporaneously supplied oral vancomycin liquids.

What does US Patent 11,638,692 claim?

The independent claims cover two related formulation classes:

Claim	Core formulation	Key limitations
1	Broad buffered formulation	Vancomycin hydrochloride, water, specified buffer, specified preservative, pH 2.5-4.5, homogeneity, stability for at least one week
5	Citric-acid formulation	Vancomycin hydrochloride, water, citric acid, specified preservative, pH 2.5-4.5, homogeneity, stability for at least one week

The dependent claims add concentration and composition limitations:

Claim 2: citric acid at 0.12% w/v.
Claim 3: sodium benzoate at 0.02% to 0.08% w/v.
Claim 4: sweetener at 0.1% to 0.3% w/v.
Claim 6: citric acid at 0.12% w/v in the claim 5 formulation.
Claim 7: sodium benzoate at 0.02% to 0.08% w/v.
Claim 8: sweetener at 0.1% to 0.3% w/v.
Claim 9: no flavoring agent.

The claims do not cover vancomycin generally. They cover a defined oral liquid dosage form and require the formulation to satisfy both compositional and performance limitations.[1]

How broad is claim 1 of US 11,638,692?

Claim 1 is broad in its excipient Markush groups but narrow in its required formulation architecture.

Required elements

A formulation must include all of the following:

Vancomycin hydrochloride.
Water.
A buffer selected from the listed compounds or compound classes.
A preservative selected from sodium benzoate, parabens, benzoic acid, potassium sorbate, benzyl alcohol, or salts thereof.
Oral administration.
A non-sterile liquid dosage form.
Homogeneity.
Stability for at least one week at ambient and refrigerated temperature.
A pH of 2.5 to 4.5.

A sweetener and flavoring agent are expressly optional. Their absence does not avoid claim 1.

Buffer scope

The buffer list includes common pharmaceutical buffering systems such as:

Citric acid and sodium citrate.
Sodium acetate.
Sodium carbonate.
Phosphate salts.
Pyrophosphate and polyphosphate salts.
Potassium phosphate and metaphosphate salts.
Magnesium, calcium, and related inorganic or organic salts.

The list is unusually heterogeneous. It includes substances that may act as buffering agents only within particular formulation conditions. A non-listed buffer, such as a different organic acid or a different phosphate salt, would fall outside the literal buffer limitation unless it is legally treated as an equivalent.

The claim also recites sodium acetate twice. The duplication does not materially expand scope.

Preservative scope

The preservative limitation is narrower than the buffer limitation. A formulation using an unlisted preservative, such as a quaternary ammonium preservative or an alternative antimicrobial system, would have a potential noninfringement position if the preservative is legally required to fall within the listed group.

The phrase “benzyl alcohol or salts thereof” may raise a construction issue because benzyl alcohol is generally used as a neutral alcohol rather than as a conventional salt-forming compound. The broader practical category remains benzyl alcohol-containing preservative systems.

What formulations are protected by claims 5 through 9?

Claims 5 through 9 create a focused citric-acid subgenus within claim 1.

Citric-acid formulation

Claim 5 requires:

Citric acid.
Water.
Vancomycin hydrochloride.
A listed preservative.
A pH of 2.5 to 4.5.
At least one week of stability at ambient and refrigerated temperature.
A homogeneous, non-sterile liquid intended for oral administration.

Claim 5 does not require sodium benzoate. It covers any listed preservative, including parabens, benzoic acid, potassium sorbate, or benzyl alcohol.

0.12% citric acid limitation

Claims 2 and 6 require citric acid at 0.12% w/v. This limitation materially narrows the claims by requiring approximately 1.2 mg/mL citric acid.

A formulation with 0.11% or 0.13% citric acid would not literally satisfy the numerical limitation, although the doctrine of equivalents could become relevant depending on prosecution history and the technical significance of the concentration.

Sodium benzoate limitation

Claims 3 and 7 cover sodium benzoate at 0.02% to 0.08% w/v. This is a concentration range of approximately 0.2 to 0.8 mg/mL.

The range is not limited to 0.12% citric acid unless claim 7 is read together with claim 5, which already requires citric acid but does not require the 0.12% concentration. Claim 3 depends from claim 1 and therefore permits any claimed buffer. Claim 7 depends from claim 5 and therefore requires citric acid.

Sweetener limitation

Claims 4 and 8 require a sweetener at 0.1% to 0.3% w/v. The claims do not identify a particular sweetener. A product using a sweetener outside that range may avoid the numerical limitation but could remain within claim 1 or claim 5 if all other limitations are met.

Flavor-free formulation

Claim 9 requires the claim 5 formulation to be free of flavoring agent. This claim is commercially relevant because oral vancomycin liquids may be supplied without flavoring or may rely on sweetener alone for palatability.

How does the “consisting of” language affect infringement?

The independent claims use “consisting of,” a closed transitional phrase. In its ordinary patent-law meaning, this language generally excludes additional ingredients that materially change the claimed formulation.

The practical effect is significant:

A formulation containing an unlisted active ingredient may fall outside the claim.
An unlisted excipient may create a noninfringement argument.
Processing aids, residual solvents, impurities, and incidental materials may not necessarily defeat the claim.
The analysis depends on whether the additional substance is materially present and whether it changes the claimed formulation.

The closed formulation language creates a potential design-around route. A competitor could evaluate a formulation using a non-listed buffer, a non-listed preservative, or an additional functional excipient. That strategy would require separate analysis under the doctrine of equivalents and the patent’s prosecution history.

The closed language does not eliminate the need to satisfy the performance limitations. A formulation with the listed ingredients but without the required stability or pH would not meet the claim as written.

What stability requirement must a competing formulation satisfy?

The claims require the liquid to be:

Homogeneous.
Stable for at least one week.
Stable at ambient temperature.
Stable at refrigerated temperature.

The claims supplied do not define:

The precise ambient temperature.
The precise refrigerated temperature.
The acceptable degradation threshold.
The required assay range.
The impurity limit.
The container-closure system.
The meaning of physical homogeneity.
Whether stability must be demonstrated in the final commercial container.

These omissions create potential claim-construction and validity issues. A patent dispute would likely focus on the specification, examples, prosecution record, and evidence showing how a skilled formulator would understand “stable” and “homogeneous.”

A competitor could challenge whether the stability limitation is sufficiently definite under 35 U.S.C. §112(b). The patent owner could respond that pharmaceutical stability has established technical meaning and that the specification provides testing methods or acceptance criteria. The strength of either position depends on the patent’s full disclosure and prosecution history, which are not contained in the supplied claims.

What is the likely infringement risk for oral vancomycin liquids?

Risk is highest for a ready-to-use liquid having the following profile:

Product characteristic	Risk under claim 1	Risk under claims 5-9
Vancomycin hydrochloride	Required	Required
Water-based liquid	Required	Required
Oral administration	Required	Required
pH 2.5-4.5	Required	Required
Citric acid buffer	Within scope	Required
Sodium benzoate preservative	Within scope	Claims 3 and 7 may apply
0.12% citric acid	Claim 2 may apply	Claim 6 may apply
Sodium benzoate 0.02-0.08% w/v	Claim 3 may apply	Claim 7 may apply
Sweetener 0.1-0.3% w/v	Claim 4 may apply	Claim 8 may apply
No flavoring agent	Not required	Claim 9 may apply
One-week ambient and refrigerated stability	Required	Required

A product containing vancomycin hydrochloride in water, citric acid, and sodium benzoate at the specified pH presents the clearest literal infringement risk. A product supplied as a dry powder for reconstitution may avoid the claims before reconstitution, but the analysis could change if the reconstituted product is the marketed dosage form and meets every claim limitation.

A compounded oral vancomycin solution may raise different issues from an FDA-approved commercial product. Patent infringement generally turns on the formulation and activity, not merely on whether the product is compounded. Regulatory exemptions and pharmacy-compounding provisions do not automatically resolve patent liability.

What patent expiration date applies to US 11,638,692?

The claims supplied do not establish the patent’s filing date, priority chain, patent-term adjustment, terminal disclaimer, or patent-term extension. Those data control the enforceable expiration date.

The statutory baseline is a term ending 20 years after the earliest effective nonprovisional filing date, subject to patent-term adjustment, terminal disclaimers, and other applicable provisions under 35 U.S.C. §154. A patent issued in 2023 does not necessarily expire in 2043.

The relevant diligence points are:

Earliest priority application.
Earliest nonprovisional application.
Continuation or divisional relationships.
Patent-term adjustment.
Terminal disclaimer.
Reexamination or post-grant proceedings.
Maintenance-fee payment status.

A reliable expiration date cannot be derived from the claims alone.

What is the Orange Book status of US 11,638,692?

A formulation patent is eligible for Orange Book listing only if it meets the FDA’s listing requirements and is associated with an approved drug product. FDA listing depends on the approved product, the NDA holder’s submission, and whether the patent claims the drug substance, drug product, or an approved method of use under 21 C.F.R. §314.53.

The supplied claims are product-formulation claims. They do not claim:

A method of treating Clostridioides difficile infection.
A dosing regimen.
A patient population.
A route other than the claimed oral formulation.
Vancomycin hydrochloride as a chemical entity.

If listed against an approved oral vancomycin product, the patent could create an ANDA certification issue. A generic applicant would generally evaluate Paragraph III or Paragraph IV certification depending on the patent’s listed status and expiration. A Paragraph IV certification could trigger patent litigation under 21 U.S.C. §355(j)(5)(B)(iii).

The claims alone do not establish whether US 11,638,692 is currently listed in the FDA Orange Book.

When could a generic launch an oral vancomycin liquid?

A generic launch pathway depends on four separate issues:

Whether an approved reference listed drug has the same dosage form.
Whether US 11,638,692 is listed against that product.
Whether other formulation, method-of-use, or regulatory exclusivity barriers remain.
Whether the ANDA applicant prevails in litigation or obtains a settlement-based launch date.

Potential launch scenarios include:

Scenario	Commercial result
No relevant listing and no enforceable blocking patent	Launch after ANDA approval
Paragraph III certification	Launch after listed patent expiration
Paragraph IV certification with no timely suit	Launch after statutory period and approval
Paragraph IV litigation with injunction	Launch depends on court outcome
Settlement with licensed entry	Launch on negotiated date
Reformulated product outside claims	Launch subject to separate infringement and approval analysis
Powder-for-reconstitution product	May avoid a ready-to-use liquid claim, subject to product-specific analysis

The most practical design-around options involve changing the buffer, preservative, pH, concentration, or physical presentation. Each option can affect palatability, microbial control, vancomycin stability, and FDA comparability requirements.

Which companies are competing in oral vancomycin?

The commercial field includes:

The NDA holder and marketer of the branded oral vancomycin product.
Generic vancomycin manufacturers.
Compounding pharmacies.
Hospital and specialty-pharmacy suppliers.
Developers of alternative oral formulations.

The principal branded benchmark in the U.S. oral vancomycin market has been FIRVANQ, an oral solution product containing vancomycin hydrochloride for preparation of an oral solution. Oral vancomycin capsules and injectable vancomycin products are not automatically substitutes for a ready-to-use liquid because they differ in dosage form, administration, patient usability, and regulatory approval status.[2]

The patent’s competitive significance is greatest where the product is marketed as a stable, ready-to-use liquid rather than as a powder requiring pharmacy reconstitution. A company selling only capsules may face a different patent profile.

How strong is the patent estate for vancomycin liquid formulations?

The strength of US 11,638,692 is mixed.

Strengths

Claim 1 covers multiple buffer classes.
The preservative group includes commonly used pharmaceutical preservatives.
The pH range is commercially practical for an acidic vancomycin formulation.
The claims target a stable non-sterile liquid, which can be commercially valuable.
Claims 5 through 9 preserve narrower citric-acid fallback positions.
The claim set captures formulations with and without sweetener or flavor.

Vulnerabilities

The stability term may require factual interpretation.
“Ambient” and “refrigerated” temperature are not numerically stated in the claims.
The claim does not define the degradation threshold for “stable.”
The “consisting of” language may permit formulation design-arounds.
Broad Markush buffer language may face anticipation or obviousness attacks if prior art discloses vancomycin liquids with acidic buffers and preservatives.
The claims do not cover every oral vancomycin dosage form.
The claims do not provide method-of-use protection.

The patent is stronger against products that closely copy the disclosed citric-acid/sodium-benzoate formulation than against products using materially different excipient systems.

What prior-art issues could affect validity?

A validity review would focus on four prior-art categories:

Earlier oral vancomycin solutions

Prior art describing vancomycin hydrochloride dissolved in water with an acidic buffer and preservative could be relevant to anticipation. The reference would need to disclose every claim element, including the pH, stability period, homogeneity, and non-sterile oral formulation.

Compounded pharmacy formulations

Compounding references, pharmacy manuals, stability studies, and publicly available formulas may be relevant if they were publicly accessible before the patent’s critical date. Their evidentiary value depends on publication date, formulation detail, and whether they establish the required stability.

FDA product materials

Earlier FDA labels, approval reviews, product specifications, and product patents may disclose relevant formulation features. Regulatory documents can be particularly important where they identify excipients, pH, storage conditions, or reconstitution stability.

Obviousness combinations

Even if no single reference anticipates the claims, an invalidity challenge could combine:

Known vancomycin oral liquid formulations.
Known acidic buffers.
Known preservatives.
Routine pH optimization.
Standard short-term stability testing.

The patent owner would likely rely on unexpected stability, improved homogeneity, preservative performance, or commercial formulation advantages to defend the claims.

What litigation, licensing, and settlement issues affect the patent?

The supplied claims do not establish any infringement action, Paragraph IV lawsuit, license, covenant not to sue, or settlement agreement involving US 11,638,692.

For transaction diligence, the relevant records are:

USPTO assignment and maintenance records.
FDA Orange Book patent-listing data.
Federal district court complaints and docket entries.
ANDA litigation filings under 21 U.S.C. §355(j).
Abbreviated New Drug Application settlement reports.
SEC filings by the patent owner or licensees.
Patent family members in the United States and foreign jurisdictions.

A license covering the patent could alter the commercial value of a formulation design-around. Conversely, an Orange Book listing without an active enforcement action may still create ANDA timing risk.

How does US 11,638,692 compare with other vancomycin patent categories?

Patent category	Relevance to this patent	Typical competitive impact
Active-ingredient patents	Low for long-marketed vancomycin hydrochloride	Usually expired or commercially weak
Oral liquid formulation patents	Direct	Can block a specific liquid composition
Powder-for-reconstitution patents	Adjacent	May affect a different product presentation
Capsule formulation patents	Limited	Do not necessarily cover liquids
Method-of-use patents	Not present in supplied claims	May create separate use-based entry barriers
Manufacturing patents	Not present in supplied claims	Can affect API or finished-dose supply
Stability or container patents	Potentially adjacent	May create additional barriers
Device or dispensing patents	Not present in supplied claims	Relevant only to specialized delivery systems

The patent should therefore be evaluated as one formulation-layer asset, not as a complete vancomycin exclusivity estate.

Key Takeaways

US 11,638,692 claims non-sterile, homogeneous oral vancomycin hydrochloride liquids.
Claim 1 requires water, a listed buffer, a listed preservative, pH 2.5-4.5, and at least one week of ambient and refrigerated stability.
Claims 5 through 9 focus on citric-acid formulations, including 0.12% citric acid, sodium benzoate at 0.02-0.08% w/v, sweetener at 0.1-0.3% w/v, and flavor-free compositions.
The strongest infringement exposure is a ready-to-use liquid containing citric acid and sodium benzoate within the claimed pH and concentration ranges.
The “consisting of” language creates potential design-around opportunities using non-listed excipients or a different formulation architecture.
The stability limitations may be central to both infringement and validity disputes.
The claims do not establish Orange Book listing, patent expiration, litigation, licensing, or settlement status.
The patent does not cover vancomycin generally, capsules, treatment methods, or manufacturing processes based on the supplied claims.

FAQs About US Patent 11,638,692

Does US 11,638,692 cover vancomycin capsules?

No. The supplied claims require a non-sterile liquid formulation for oral administration. A vancomycin capsule would not meet the liquid limitation.

Does a formulation with potassium sorbate fall within the patent?

Potentially. Potassium sorbate is one of the expressly listed preservatives. The formulation must also satisfy the vancomycin, water, buffer, pH, homogeneity, and stability limitations.

Can a competitor avoid claim 9 by adding flavor?

Potentially, but adding flavor would avoid only claim 9. It would not necessarily avoid claim 5 or other claims if the formulation still contains the required ingredients and satisfies the pH and stability limitations.

Does the patent cover a formulation with a pH of 5.0?

No literal infringement under the supplied claims is apparent because the claimed pH range ends at 4.5. The effect of a pH of 5.0 would require separate analysis under the doctrine of equivalents.

Is FDA approval required to infringe the patent?

No. Patent infringement and FDA approval are separate legal questions. A formulation can raise patent issues even if it is compounded, investigational, or not yet approved, subject to applicable statutory safe harbors and factual circumstances.

References

United States Patent No. 11,638,692, claims 1-9 (2023).
U.S. Food and Drug Administration. (n.d.). FIRVANQ (vancomycin hydrochloride) for oral solution prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
U.S. Code, 21 U.S.C. §355(j).
U.S. Code, 35 U.S.C. §§102, 103, 112, 154.
Code of Federal Regulations, 21 C.F.R. §314.53.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Azurity	FIRVANQ KIT	vancomycin hydrochloride	FOR SOLUTION;ORAL	208910-001	Jan 26, 2018	AA	RX	Yes	Yes	11,638,692	⤷ Start Trial	Y				⤷ Start Trial
Azurity	FIRVANQ KIT	vancomycin hydrochloride	FOR SOLUTION;ORAL	208910-002	Jan 26, 2018	AA	RX	Yes	Yes	11,638,692	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2015229069	⤷ Start Trial
Canada	2941867	⤷ Start Trial
China	106573037	⤷ Start Trial
China	122075668	⤷ Start Trial
Denmark	4000628	⤷ Start Trial
European Patent Office	3145527	⤷ Start Trial
European Patent Office	4000628	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 11,638,692